The field of this invention is related to drilling jar tools for applying a jarring blow to an object stuck in a well such as a stuck pipe or fish.
Heretofore, drilling jar tool systems including means for hydraulically developing an up-blow and means for mechanically developing a down-blow to an object stuck in a well have conventionally been constructed in a single structure. See, for example, U.S. Pat. No. 3,853,187. Such two-way hydromechanical jars, however, suffer from the disadvantage of having relatively long lengths required for housing the respective operational parts of the hydraulic and mechanical means provided within telescopically related longitudinally movable inner and outer tubular members. The relatively long length is disadvantageous inasmuch as it subjects the working parts of the tool to excessive bending moments which may be encountered in the well which may damage or jam such working parts. Moreover, due to the relatively long length such tools have heretofore been constructed with relatively thick-walled tubular elements which are substantially inflexible subjecting such tools to sticking or jamming in many well bores such as slant well bores.
Additionally, these relatively long single structure jarring tools are difficult to handle during the running of a drill string and are extremely cumbersome to transport.